From a precursory look at the UCAT, it seems that this is the parallel between this and the UMAT:
Old section 1 UMAT → Verbal Reasoning, Decision Making, probably Quantitative Reasoning as well
Old section 3 UMAT → Abstract Reasoning
Old Section 2 UMAT → gone
Out of the blue → Situation Judgment Test
For those who are reading this for the first time, while the UMAT is different from the UCAT, it's rather unsurprising that at least some of the domains tested are conserved.
Going by this, if you wish to familiarise yourself with the old Section 1 and Section 3 questions for some good practice this may help with your efforts to prepare for this.
MSO's UMAT Questions is still there for anyone who wants to use the old MSO UMAT questions, although the Section 2 questions might be less relevant now.
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Thoughts on the transition to the UCAT:
1. The first, and most concerning, thought to me is that there was a study in the UMAT that showed that there was a male preponderance for higher scores in Section 1 and Section 3 and a female preponderance for higher scores in Section 2. While these scores are on a large cohort level only, the difference was present and I believe statistically significant.
With the old Section 2 having no equivalent in the UCAT, I wonder if the male preponderance for marginally higher scores will be reflected in this, and whether it is appropriate to have a test that selects against any gender.
2. More accessibility to the exam via the internet/reliability of a non-paper test
To be honest, I think any improvement to the accessibility of the test is a welcome change. However the first warning sign to me is the fact that the provider of this test is Pearson Vue. For those not well versed in this this is the company at the centre of the RACP Basic Physician Examination kerfuffle earlier this year (goodness knows how they managed to get the contract with the UCAT Consortium...). Given the lack of stopgaps in that previous exam, and the fact that you can only take the test ONCE per year, I can see this going very, very bad (imagine what happens if you take the test and then your internet disconnects and doesn't reconnect until your allocated time is over!)